1. Field
This application relates to devices for controlling depth of penetration of rotary cutting tools into the work-piece in a manner that avoids any marring or damage to work-piece surface.
2. Prior Art
Depth limiting devices for rotary cutting tool, particularly for drill bits and countersink tools, having contacting structures providing free rotation relative to rotary cutting tool are known in the art.
U.S. Pat. No. 5,795,110 describes a drill stop collar having an independently rotatable plastic cap covering lower end of the stop collar. A device is selectively mounted along the drill bit at a position that limits the depth of penetration of the rotary cutting tool into the work-piece below then predetermined depth. A cap ceases to rotate when basically flat surface of the contacting portion of the cap comes into contact with work-piece and prevents surface of the work-piece from being marred.
U.S. Pat. No. 7,258,513 discloses a depth limiting device which includes a spindle and stop sleeve that is in the form of a cylindrical shell having a first end with opening and a contacting portion extending along the periphery of the opening in the direction of working section of the drill bit. A spindle extending axially through the stop sleeve includes a first end for attaching to a drilling machine, and a second end integrally formed as countersink tool with central bore for receiving and selectively fixing therein the drill bit, thereby providing adjustment of depth of penetration into the work-piece by the drill bit. Second end of the stop sleeve is permanently fixed on spindle in longitudinal position and freely axially rotates around the spindle and ceases to rotate when it contacts the work-piece without marring or otherwise damaging the work-piece. A stop sleeve which serves as abutment, limits further then predetermined penetration of the countersink tool and drill bit into the work-piece. Internal space of the stop sleeve communicates with opening, allowing debris to be inside the stop sleeve and reducing the presence of debris between contacting portion of stop sleeve and work-piece, thereby providing the accuracy of drilling. In addition, adjustment of penetration of the countersink tool into the work-piece provided by attachable to the contacting portion of stop sleeve of depth-adjusting members with varying thicknesses.
DE Pat. No. 10154434 describes a stop device having spindle with axial bore for receiving and longitudinally adjusting the drill bit and stop sleeve, which freely rotates with respect to spindle. Countersink tool which is a separate part of the device, has central aperture or bore for receiving the drill bit therein. Countersink tool can be slid along the drill bit to the required position and be secured by set screw. Thereby device provides depth adjustment for the drill bit and also for the countersink tool. However, if operator adjusts depth of penetration of the drill bit, as result it will further be necessary to readjust the countersink tool, since the letter is attached to the drill bit.
EP2093001 discloses device with a spindle including a first end for attaching to a drilling machine, and a second end integrally formed as a countersink tool with central bore for receiving and selectively fixing therein the drill bit thereby providing adjustment of the depth of penetration into the work-piece by drill bit. The spindle includes an external threaded portion for threaded engagement with a hollow elongated cylindrical member to which in turn rotatably attached is the stop sleeve. The operator screws the cylindrical member in or out relative to the spindle and cylindrical member coupled with stop sleeve axially moves relative to spindle, thereby exposing desirable distance between cutting edges of the countersink tool and contacting portion of the stop sleeve. When predetermined position is attained, cylindrical member is secured relative to spindle by set screw which extends through the body of cylindrical member to engage the spindle. Such design of the depth limiting device allows an operator to adjust the depth of penetration of the drill bit without disturbing the position of the countersink tool relative to stop sleeve.
It can be seen that U.S. Pat. No. 7,258,513, DE10154434 and EP2093001 include intermediate member such as a spindle having central bore, which correspondingly fits certain diameter of the drill bit and for a range of diameters of drill bits will be necessary a range of suitable devices. Moreover, spindles are preferably composed of metal, which requires different types of metalworking processes. Everything aforementioned ads complexity and increase the cost to manufacture the devices.